Re: [Xen-devel] [PATCH] passthrough: give XEN_DOMCTL_test_assign_device more sane semantics

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 21/06/17 11:08, Jan Beulich wrote:
> So far callers of the libxc interface passed in a domain ID which was
> then ignored in the hypervisor. Instead, make the hypervisor honor it
> (accepting DOMID_INVALID to obtain original behavior), allowing to
> query whether a device is assigned to a particular domain. Ignore the
> passed in domain ID at the libxc layer instead, in order to not break
> existing callers. New libxc functions would need to be added if callers
> wanted to leverage the new functionality.

I don't think your modified description matches the name of the call at all.

It looks like the callers expect "test_assign_device" to answer the
question: "Can I assign a device to this domain"?

It looks like it's meant to be used in XSM environments, to allow a
policy to permit or forbid specific guests to have access to specific
devices.  On a default (non-XSM) system, the answer to that question
doesn't depend on the domain it's being assigned to, but only whether
the device is already assigned to another domain; but on XSM systems the
logic can presumably be more complicated.

That sounds like a perfectly sane semantic to me, and this patch removes
that ability.

I think if you want a hypercall that answers the question, "Is device X
assigned to domain Y", I think you should add a new one with a name more
like, "test_device_is_assigned_to" or something.

 -George


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel